The present invention relates generally to systems for removing human waste from a toilet bowl by vacuum pressure and rinsing it thereafter, and more particularly to a system in which the discharge valve, water valve, and controller valve are operated by means of differential pressure.
In a conventional toilet system, the toilet bowl is connected to a holding sump by means of a drain pipe. Human waste in the toilet bowl, be it liquid or solid, is evacuated to the drain pipe, and thereby to the holding sump when the water already in the bowl is evacuated to the drain pipe by gravity, and new water is flushed into the bowl to rinse it. The waste material in the holding sump, in turn, may be transported to a collection tank by a number of means, including gravity flow, positive pressure flow, or vacuum pressure, depending upon the topography of the terrain. U.S. Pat. No. 4,179,371 issued to Foreman et al. discloses a vacuum transport system, using two-phase flow and equalized pressure communication throughout the transport conduit generally upon completion of a vacuum transport cycle.
The source of vacuum pressure may also be communicated directly to the toilet bowl so that the waste matter is withdrawn under the influence of differential pressure to the holding sump or directly to the vacuum transport conduit. Such a vacuum toilet system may be more compact in design (and thereby suitable for mobile settings such as airplanes and trains) because of smaller pipe requirements, flexibility of routing due to lift characteristics (vacuum transport conduit may be routed over, under, or around obstacles unlike gravity systems), and it conserves rinse water, because water is not required to provide positive pressure for pushing the waste material out of the toilet bowl during discharge. U.S. Pat. No. 3,922,730 issued to Kemper; U.S. Pat. No. 3,995,328 issued to Carolan et al.; U.S. Pat. No. 4,199,828 issued to Hellers; and U.S. Pat. No. 4,276,663 issued to Gensurowsky, as well as U.K. Published Application Nos. 2,194,260 and 2,203,461 provide examples of such vacuum toilets and systems.
Discharge valves in such systems have used simple flap doors which are opened either by means of the weight of the waste material (Hellers, or U.S. Pat. No. 4,184,506 issued to Varis et al.), or by means of differential pressure (U.S. Pat. No. 4,296,772 issued to Nilsson). However, such closure mechanisms may easily become lodged in the open position to impair the return of a vacuum pressure condition to the vacuum transport conduit downstream of the flap valve.
In the alternative, purely mechanical closure means have been incorporated into a discharge valve, such as a plunger operated by a pivotable latch (U.S. Pat. No. 4,621,379 issued to Kilpi), a reciprocating closure which pinches a flexible hose (U.S. Pat. No. 4,376,314 issued to Iwans; and U.S. Pat. No. 4,783,859 issued to Rozenblatt et al.), or a rotated disk which seals and unseals an aperture (U.S. Pat. No. 4,713,847 issued to Oldfelt et al.). Such purely mechanically operated discharge valves, though, are subject to excessive wear and tear, and provide imperfect seals of the vacuum transport conduit downstream thereof.
Therefore, resort has been made to discharge valve closure members having a chamber defined by a diaphragm connected to piston rod to seal the valve upon the application of differential pressure across the diaphragm. (See, e.g. U.S. Pat. No. 3,788,338 issued to Burns; U.S. Pat. No. 3,807,431 issued to Svanteson; U.S. Pat. No. 4,376,315 issued to Badger et al.; U.S. Pat. No. 4,041,554 issued to Gregory et al.; and U.K. Patent No. 1,538,820 issued to Electrolux GmbH.) But, the diaphragm is easily ruptured against the internal valve body during closure, and the valve housing is space-consuming due to the tapered profile of the housing required to assist in the application of differential pressure to differing cross-sectional areas to overcome the force applied by a spring bearing against a portion of the piston rod adjacent to the diaphragm. The use of a diaphragm activated reciprocating pin in U.S. Pat. No. 4,057,076 issued to Varis et al. to dislodge a ball which closes a valve opening provides an extremely inefficient alternative.
As for controller mechanisms used to activate discharge valves in vacuum toilet systems, floats (Svanteson and Varis), solenoids (Badger and Burns), pressure switches (U.S. Pat. No. 4,520,513 issued to Raupuk, Jr. et al.), electromechanical devices (Rozenblatt), and simple two-position dial valves (Electrolux) have been used. An extremely complicated push button actuator valve is disclosed in Gregory.